Method for handling of a RRC connection request message of a remote UE by a relay UE in wireless communication system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for handling of a RRC connection request message of a remote UE by a Relay UE in wireless communication system, the method comprising: receiving NAS information for establishing RRC connection of the remote UE from a remote UE which is configured to connect to the relay UE via sidelink in state that both of the remote UE and the relay UE are in RRC idle states, transmitting a RRC connection request message with an identity of the remote UE to an eNB, when a NAS layer of the relay UE triggers only service request for the remote UE; transmitting a RRC connection setup message for the remote UE to the remote UE; and transmitting a RRC connection setup complete message with the received NAS information of the remoter UE to the eNB.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/KR2018/001551, filed on Feb. 6,2018, which claims the benefit of U.S. Provisional Application No.62/454,904, filed on Feb. 6, 2017. The disclosures of the priorapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for handling of a RRC connection requestmessage of a remote UE by a Relay UE in wireless communication systemand a device therefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

DISCLOSURE OF INVENTION Technical Problem

An object of the present invention devised to solve the problem lies ina method and device for handling of a RRC connection request message ofa remote UE by a Relay UE in wireless communication system.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Solution to Problem

The object of the present invention can be achieved by providing amethod for User Equipment (UE) operating in a wireless communicationsystem as set forth in the appended claims.

In another aspect of the present invention, provided herein is acommunication apparatus as set forth in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects of Invention

In this invention, it is presented about models the relay UE handles theRRC connection request message including NAS message. The methodscomprises of two parts. The first part is what AS layer of the relay UEinforms to NAS layer of the relay UE and how AS layer of the relay UEhandles the received RRC connection request message upon receiving theRRC connection request message from the remote UE. The second part ishow NAS layer of the relay UE triggers NAS message transmission.

It will be appreciated by persons skilled in the art that the effectsachieved by the present invention are not limited to what has beenparticularly described hereinabove and other advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention;

FIG. 6 is a conceptual diagram for sidelink communication;

FIG. 7a is a diagram for protocol stack for the user plane of sidelinkcommunication, FIGS. 7b and 7c are diagrams for protocol stack for thecontrol plane of sidelink communication;

FIGS. 8a to 8d are examples for radio protocol stacks for Layer-2evolved UE-to-Network relay; and

FIGS. 9 to 11 are conceptual diagrams for handling of a RRC connectionrequest message of a remote UE by a Relay UE in wireless communicationsystem according to embodiments of the present invention; and

FIG. 12 is a conceptual diagram for performing a RRC connectionestablishment procedure depending on sidelink condition by a remote UEin wireless communication system according to embodiments of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor(110) and RF module (transceiver; 135). The DSP/microprocessor (110) iselectrically connected with the transceiver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

FIG. 6 is a conceptual diagram for sidelink communication.

Sidelink comprises sidelink discovery, sidelink communication and V2Xsidelink communication between UEs. Sidelink uses uplink resources andphysical channel structure similar to uplink transmissions. However,some changes, noted below, are made to the physical channels. Sidelinktransmission uses the same basic transmission scheme as the ULtransmission scheme. However, sidelink is limited to single clustertransmissions for all the sidelink physical channels. Further, sidelinkuses a 1 symbol gap at the end of each sidelink subframe. For V2Xsidelink communication, PSCCH and PSSCH are transmitted in the samesubframe. The sidelink physical layer processing of transport channelsdiffers from UL transmission in the following steps: for PSDCH andPSCCH, the scrambling is not UE-specific; and modulation of 64 QAM and256 QAM is not supported for sidelink PSCCH is mapped to the sidelinkcontrol resources. PSCCH indicates resource and other transmissionparameters used by a UE for PSSCH. For PSDCH, PSCCH and PSSCHdemodulation, reference signals similar to uplink demodulation referencesignals are transmitted in the 4-th symbol of the slot in normal CP andin the 3rd symbol of the slot in extended cyclic prefix. The sidelinkdemodulation reference signals sequence length equals the size (numberof sub-carriers) of the assigned resource. For V2X sidelinkcommunication, reference signals are transmitted in 3rd and 6th symbolsof the first slot and 2nd and 5th symbols of the second slot in normalCP. For PSDCH and PSCCH, reference signals are created based on a fixedbase sequence, cyclic shift and orthogonal cover code. For V2X sidelinkcommunication, cyclic shift for PSCCH is randomly selected in eachtransmission.

Sidelink communication is a mode of communication whereby UEs cancommunicate with each other directly over the PC5 interface. Thiscommunication mode is supported when the UE is served by E-UTRAN andwhen the UE is outside of E-UTRA coverage. Only those UEs authorised tobe used for public safety operation can perform sidelink communication.

In order to perform synchronization for out of coverage operation UE(s)may act as a synchronization source by transmitting SBCCH and asynchronization signal. SBCCH carries the most essential systeminformation needed to receive other sidelink channels and signals. SBCCHalong with a synchronization signal is transmitted with a fixedperiodicity of 40 ms. When the UE is in network coverage, the contentsof SBCCH are derived from the parameters signaled by the eNB. When theUE is out of coverage, if the UE selects another UE as a synchronizationreference, then the content of SBCCH is derived from the received SBCCH;otherwise UE uses pre-configured parameters. SIB18 provides the resourceinformation for synchronization signal and SBCCH transmission. There aretwo pre-configured subframes every 40 ms for out of coverage operation.UE receives synchronisation signal and SBCCH in one subframe andtransmit synchronisation signal and SBCCH on another subframe if UEbecomes synchronization source based on defined criterion.

UE performs sidelink communication on subframes defined over theduration of Sidelink Control period. The Sidelink Control period is theperiod over which resources allocated in a cell for sidelink controlinformation and sidelink data transmissions occur. Within the SidelinkControl period the UE sends sidelink control information followed bysidelink data. Sidelink control information indicates a Layer 1 ID andcharacteristics of the transmissions (e.g. MCS, location of theresource(s) over the duration of Sidelink Control period, timingalignment).

The UE performs transmission and reception over Uu and PC5 with thefollowing decreasing priority order in case Sidelink Discovery Gap isnot configured:

i) Uu transmission/reception (highest priority);

ii) PC5 sidelink communication transmission/reception;

iii) PC5 sidelink discovery announcement/monitoring (lowest priority).

The UE performs transmission and reception over Uu and PC5 with thefollowing decreasing priority order in case Sidelink Discovery Gap isconfigured:

i) Uu transmission/reception for RACH;

ii) PC5 sidelink discovery announcement during a Sidelink Discovery Gapfor transmission;

iii) Non-RACH Uu transmission;

iv) PC5 sidelink discovery monitoring during a Sidelink Discovery Gapfor reception;

v) Non-RACH Uu reception;

vi) PC5 sidelink communication transmission/reception.

FIG. 7a is a diagram for protocol stack for the user plane of sidelinkcommunication, FIGS. 7b and 7c are diagrams for protocol stack for thecontrol plane of sidelink communication;

FIG. 7a shows the protocol stack for the user plane, where PDCP, RLC andMAC sublayers (terminate at the other UE) perform the functions listedfor the user plane. The Access Stratum protocol stack in the PC5interface consists of PDCP, RLC, MAC and PHY as shown below in FIG. 7 a.

User plane details of sidelink communication: i) there is no HARQfeedback for sidelink communication; ii) RLC UM is used for sidelinkcommunication; iii) a receiving UE needs to maintain at least one RLC UMentity per transmitting peer UE; iv) a receiving RLC UM entity used forsidelink communication does not need to be configured prior to receptionof the first RLC UMD PDU; v) a ROHC Unidirectional Mode is used forheader compression in PDCP for sidelink communication.

A UE may establish multiple logical channels. LCID included within theMAC subheader uniquely identifies a logical channel within the scope ofone Source Layer-2 ID and Destination Layer-2 ID combination. Parametersfor logical channel prioritization are not configured. The Accessstratum (AS) is provided with the PPPP of a protocol data unittransmitted over PC5 interface by higher layer. There is a PPPPassociated with each logical channel.

A UE does not establish and maintain a logical connection to receivingUEs prior to one-to-many a sidelink communication. Higher layerestablishes and maintains a logical connection for one-to-one sidelinkcommunication including ProSe UE-to-Network Relay operation.

The Access Stratum protocol stack for SBCCH (Sidelink Broadcast ControlChannel) in the PC5 interface consists of RRC, RLC, MAC and PHY as shownbelow in FIG. 7 b.

The control plane for establishing, maintaining and releasing thelogical connection for one-to-one sidelink communication is shown inFIG. 7 c.

FIGS. 8a to 8d are examples for radio protocol stacks for Layer-2evolved UE-to-Network relay.

In FIGS. 8a to 8d , a protocol architecture for supporting Layer 2evolved UE-to-Network Relay UE is given for the user plane and thecontrol plane.

For protocol architecture for the user plane and control plane, relayingis performed above RLC sublayer. The evolved ProSe Remote UE's userplane and control plane data are relayed above RLC via the evolved ProSeUE-to-Network Relay UE from the evolved ProSe Remote UE to network andvice versa. Uu PDCP and RRC are terminated between the evolved ProSeRemote UE and the eNB while RLC, MAC and PHY and the non-3GPP transportlayers are terminated in each link (i.e. the link between the evolvedProSe Remote UE and the evolved ProSe UE-to-Network Relay UE and thelink between the evolved ProSe UE-to-Network Relay UE and the eNB). Theuser plane protocol stack and the control plane protocol stack when PC5is used between the evolved ProSe remote UE and the evolved ProSeUE-to-Network Relay UE is shown in FIG. 8a and FIG. 8b . The user planeprotocol stack and the control plane protocol stack when non-3GPP accessis used between the evolved ProSe remote UE and the evolved ProSeUE-to-Network Relay UE is shown in FIG. 8c and FIG. 8 d.

When PC5 interface is used between the evolved ProSe remote UE and theevolved ProSe UE-to-Network Relay UE, by introducing a relay UE forUE-to-network relay, a Remote UE transmits data to an eNB via the RelayUE, and the eNB transmits data to the Remote UE via the Relay UE. I.e.,the Relay UE relays data to/from eNB.

As data transfer between the remote UE and the Relay UE is ProSecommunication, the Relay UE is communicating with the Remote UE over PC5interface. In the meantime, as data transfer between the Relay UE andthe eNB is a normal uplink/downlink (Uu) communication, the Relay UE iscommunicating with the eNB over Uu interface.

A ProSe UE-to-Network Relay provides a generic L3 forwarding functionthat can relay any type of IP traffic between the Remote UE and thenetwork. One-to-one and one-to-many sidelink communications are usedbetween the Remote UE(s) and the ProSe UE-to-Network Relay. For bothRemote UE and Relay UE only one single carrier (i.e., Public SafetyProSe Carrier) operation is supported (i.e., Uu and PC5 should be samecarrier for Relay/Remote UE). The Remote UE is authorised by upperlayers and can be in-coverage of the Public Safety ProSe Carrier orout-of-coverage on any supported carriers including Public Safety ProSeCarrier for UE-to-Network Relay discovery, (re)selection andcommunication. The ProSe UE-to-Network Relay is always in-coverage ofEUTRAN. The ProSe UE-to-Network Relay and the Remote UE perform sidelinkcommunication and sidelink discovery.

A ProSe UE-to-Network Relay performing sidelink communication for ProSeUE-to-Network Relay operation has to be in RRC_CONNECTED. Afterreceiving a layer-2 link establishment request or TMGI monitoringrequest (upper layer message) from the Remote UE, the ProSeUE-to-Network Relay indicates to the eNB that it is a ProSeUE-to-Network Relay and intends to perform ProSe UE-to-Network Relaysidelink communication. The eNB may provide resources for ProSeUE-to-Network Relay communication.

The Remote UE can decide when to start monitoring for ProSeUE-to-Network Relay discovery. The Remote UE can transmit ProSeUE-to-Network Relay discovery solicitation messages while in RRC_IDLE orin RRC_CONNECTED depending on the configuration of resources for ProSeUE-to-Network Relay discovery. The eNB may broadcast a threshold, whichis used by the Remote UE to determine if it can transmit ProSeUE-to-Network Relay discovery solicitation messages, to connect orcommunicate with ProSe UE-to-Network Relay UE. The RRC_CONNECTED RemoteUE, uses the broadcasted threshold to determine if it can indicate toeNB that it is a Remote UE and wants to participate in ProSeUE-to-Network Relay discovery and/or communication. The eNB may provide,transmission resources using broadcast or dedicated signalling andreception resources using broadcast signalling for ProSe UE-to-NetworkRelay Operation. The Remote UE stops using ProSe UE-to-Network Relaydiscovery and communication resources when RSRP goes above thebroadcasted threshold.

The Remote UE performs radio measurements at PC5 interface and uses themfor ProSe UE-to-Network Relay selection and reselection along withhigher layer criterion. A ProSe UE-to-Network Relay is consideredsuitable in terms of radio criteria if the PC5 link quality exceedsconfigured threshold (pre-configured or provided by eNB). The Remote UEselects the ProSe UE-to-Network Relay, which satisfies higher layercriterion and has best PC5 link quality among all suitable ProSeUE-to-Network Relays. Traffic of one or multiple evolved ProSe RemoteUEs may be mapped to a single DRB of Uu interface of the evolved ProSeUE-to-Network Relay UE. Multiple Uu DRBs may be used to carry traffic ofdifferent QoS classes, for one or multiple evolved ProSe Remote UEs. Itis also possible to multiplex traffic of evolved ProSe UE-to-NetworkRelay UE itself onto the Uu DRB, which is used to relay traffic to/fromevolved ProSe Remote UEs. How the mapping of the traffic betweensidelink bearers and Uu bearers is done is up to the eNB implementationand the mapping is configured in evolved ProSe UE-to-Network Relay UE bythe eNB. An adaptation layer over Uu is supported to identify theevolved ProSe Remote UE/evolved ProSe UE-to-Network Relay UE and thecorresponding.

Within a Uu DRB, different evolved ProSe Remote UEs and differentbearers of the evolved ProSe Remote UE are indicated by additionalinformation included in adaptation layer header which is added to PDCPPDU. An adaptation layer is supported over non-3GPP access for the shortrange link between the evolved ProSe Remote UE and the evolved ProSeUE-to-Network Relay UE. Adaptation layer header is added to PDCP PDU.

In case of L3 relay forwarding, the remote UE is allowed to stay in RRCidle state. However, when the remote UE and relay UE is in RRC idlestate, the L2 relay UE and the remote UE has to establish RRC connectionif the remote UE has MO data and need to transmit to the network. Howthe relay UE handles the received RRC connection request needs to bemade.

More specifically, when the remote UE and relay UE is in RRC idle state,if there is no data for the relay UE which only forwards data of remoteUE to a network, there is a need for a solution to complete RRCconnection establishment of remote UE without a connection between relayUE and core network while establishing RRC connection between the relayUE and RAN node (e.g. eNB).

In the methods below, it is presented about models the relay UE handlesthe RRC connection request message including NAS message. The methodscomprises of two parts. The first part is what AS layer (e.g. adaptationlayer) of the relay UE informs to NAS layer of the relay UE and how ASlayer of the relay UE handles the received RRC connection requestmessage upon receiving the RRC connection request message from theremote UE. The second part is how NAS layer of the relay UE triggers NASmessage transmission.

In the methods below, it is assumed that i) the remote UE and the relayUE is in RRC idle state, and ii) the relay UE is L2 relay.

Regarding what AS layer of the relay UE informs to NAS layer of therelay UE and how AS layer of the relay UE handles the received RRCconnection request message upon receiving the RRC connection requestmessage from the remote UE, there is two models.

First option is that, upon receiving RRC connection request message ofthe remote UE, optionally including NAS information, AS layer (e.g.adaption layer) of the relay UE in RRC idle state informs to the upperlayer that the RRC message or NAS message is received and the AS layerstores the received RRC connection request message (Model 1).

Second option is that, upon receiving RRC message including NASinformation of the remote UE (e.g. Service request, S-TMSI, cause valueor call type), AS layer (e.g. adaption layer) of the relay UE in RRCidle state forwards to the upper layer the NAS information and the ASlayer stores or doesn't store the received NAS information (Model 2).

Regarding how NAS layer of the relay UE triggers NAS message (e.g.service request) transmission upon receiving RRC message or NASinformation from the AS layer of the relay UE, there is three models.

First option is that the NAS layer of the relay UE always provides NASmessage of the relay UE itself to AS layer (Model A), and second optionis that NAS layer of the relay UE provides the received NAS message ofthe remote UE to AS layer without any NAS message of the relay UE (ModelB). And third option is that the NAS layer of the relay UE provides theNAS message of the relay UE and the received NAS message of the remoteUE to AS layer (Model C).

FIG. 9 is a conceptual diagram for handling of a RRC connection requestmessage of a remote UE by a Relay UE in wireless communication systemaccording to embodiments of the present invention.

This example for combination of Model 1 and Model A.

When a NAS layer of the remote UE sends the NAS message to the RRC layerof the remote UE, a RRC layer of the remote UE sends RRC connectionrequest message to the connected relay UE via sidelink (S901).

Additionally, adaption layer of the remote UE includes the indicationthat SRB message is included or SRB type (e.g. SRB0, 1, 2).

Additionally, the RRC layer of the remote UE provides the cause value orcall type to the adaption layer of the remote UE. In this case, theadaption layer of the remote UE includes the cause value and/or calltype in header and sends to the connected relay UE. The included causevalue and/or call type is sent together with the RRC connection requestmessage.

If the relay UE is in RRC idle state, upon receiving the RRC connectionrequest message, the adaptation layer of the relay UE knows whether RRCconnection request message is received from the remote UE by theinformation added by adaption layer of the remote UE and informs to theupper layer (e.g. NAS layer of the relay UE) that RRC connection requestmessage is received if RRC connection request message is received(S903).

The adaption layer of the relay UE stores the received RRC connectionrequest message (S905).

Preferably, if call type and/or cause value is received, the adaptationlayer of the relay UE informs to the upper layer (e.g. NAS layer of therelay UE) the cause value and/or call type.

The NAS layer of the relay UE triggers service request and sends thereceived cause value and call type to AS layer (i.e. RRC layer) of therelay UE (S907).

The RRC layer of the relay UE sends the RRC connection request messageof the relay UE itself, the RRC layer of the relay UE receives RRCconnection setup message from a network (S909).

After RRC connection is setup (i.e. RRC connection setup message isreceived), the relay UE forwards the received RRC connection requestmessage of the remote UE to the eNB. Or after sending RRC connectionsetup complete message, the relay UE forwards the received RRCconnection message of the remote UE to the eNB (S911).

After RRC connection is setup (i.e. RRC connection setup message isreceived) by the remote UE, the remote UE sends the RRC connection setupcomplete message to the eNB via relay UE (S913).

Preferably, the relay UE just forwards the received RRC connection setupcomplete message in L2.

FIG. 10 is a conceptual diagram for handling of a RRC connection requestmessage of a remote UE by a Relay UE in wireless communication systemaccording to embodiments of the present invention.

This example for combination of Model 2 and Model A.

Further, in this example, instead of reusing existing RRC connectionrequest message and RRC connection setup complete message, one RRCmessage is used to include S-TMSI, cause value, the fields in theexisting Msg.5 (RRC connection setup complete). Then, S913 which shownin FIG. 9 can be skipped. With this, it is possible to reduce the numberof message exchanges so that the remote UE and relay UE are allowed tosave the battery.

When a NAS layer of the remote UE sends the NAS message to the RRC layerof the remote UE, the RRC layer of the remote UE sends NAS informationfor establishing RRC connection in e.g. RRC connection request messageto the connected relay UE via sidelink (S1001).

Preferably, the RRC connection request message includes NAS information(e.g. S-TMSI of the remote UE, cause value, the fields in the existingMsg.5 (RRC connection setup complete message)).

Additionally, adaption layer of the remote UE includes an indicationthat NAS information is included in the RRC connection request message.

Additionally, the RRC layer of the remote UE provides the cause value orcall type to the adaption layer of the remote UE. In this case, theadaption layer of the remote UE includes the cause value and/or calltype in header and sends to the connected relay UE. The included causevalue and/or call type is sent together with the RRC connection requestmessage.

If the relay UE is in RRC idle state, upon receiving the RRC connectionrequest message including the NAS information, the adaptation layer ofthe relay UE informs to the upper layer (e.g. NAS layer of the relay UE)that RRC connection request message is received by the includedinformation added by application layer of the remote UE (S1003).

In addition, the adaptation layer of the relay UE forwards the NASinformation in the RRC connection request message to the NAS layer ofthe relay UE (S1005).

Preferably, if call type and/or cause value is received, the adaptationlayer of the relay UE informs to the upper layer (e.g. NAS layer of therelay UE) the cause value and/or call type.

Preferably, the forwarding to NAS layer the received NAS information canbe triggered only when adaption layer indicates that NAS information isincluded in the RRC connection request message.

Preferably, the RRC layer of the relay UE de-capsulate the RRCconnection request message and forwards the only NAS part of the RRCconnection request message.

The adaption layer of the relay UE stores or doesn't the received RRCconnection request message (S1007).

The NAS layer of the relay UE triggers service request and sends thereceived cause value and call type to AS layer (i.e. RRC layer) of therelay UE (S1009).

The RRC layer of the relay UE sends the RRC connection request messageof the relay UE itself, the RRC layer of the relay UE receives RRCconnection setup message from a network (S1011).

After RRC connection is setup (i.e. RRC connection setup message isreceived), the relay UE forwards the received RRC connection message ofthe remote UE to the network. Or after sending RRC connection setupcomplete message, the relay UE forwards the received RRC connectionmessage of the remote UE to RAN node (e.g. eNB) (S1013).

And the network transmits RRC connection setup message of the remote UEvia the relay UE (S1015). In this case, after RRC connection is setup(i.e. RRC connection setup message is received) by the remote UE, theremote UE doesn't need to send the RRC connection setup complete messageto the eNB via relay UE. This is because the information related to RRCconnection setup complete message has already been transmitted throughstep S1001.

FIG. 11 is a conceptual diagram for handling of a RRC connection requestmessage of a remote UE by a Relay UE in wireless communication systemaccording to embodiments of the present invention.

This example for combination of Model 2 and Model B/C.

Further, in this example, instead of reusing existing RRC connectionrequest message and RRC connection setup complete message, one RRCmessage is used to include S-TMSI, cause value, the fields in theexisting Msg.5 (RRC connection setup complete). Then, S913 which shownin FIG. 9 can be skipped. With this, it is possible to reduce the numberof message exchanges so that the remote UE and relay UE are allowed tosave the battery.

When a NAS layer of the remote UE sends the NAS message to the RRC layerof the remote UE, RRC layer of the remote UE sends NAS information forestablishing RRC connection ine.g. RRC connection request message to theconnected relay UE via sidelink (S1101).

Preferably, the RRC connection request message includes NAS information(e.g. S-TMSI of the remote UE, cause value, the fields in the existingMsg.5 (RRC connection setup complete message)).

Additionally, adaption layer of the remote UE includes an indicationthat NAS information is included in the RRC connection request message.

Additionally, the RRC layer of the remote UE provides the cause value orcall type to the adaption layer of the remote UE. In this case, theadaption layer of the remote UE includes the cause value and/or calltype in header and sends to the connected relay UE. The included causevalue and/or call type is sent together with the RRC connection requestmessage.

If the relay UE is in RRC idle state, upon receiving the RRC connectionrequest message including the NAS information, the adaptation layer ofthe relay UE forwards NAS information in the RRC connection requestmessage to the NAS layer of the relay UE (S1103).

Preferably, if call type and/or cause value is received, the adaptationlayer of the relay UE informs to the upper layer (e.g. NAS layer of therelay UE) the cause value and/or call type.

Preferably, the forwarding to NAS layer the received NAS information canbe triggered only when adaption layer indicates that NAS information isincluded in the RRC connection request message.

Preferably, the RRC layer of the relay UE de-capsulate the RRCconnection request message and forwards the only NAS part of the RRCconnection request message.

The adaption layer of the relay UE stores or doesn't store the receivedRRC connection request message (S1105).

The NAS layer of the relay UE provides service request for relay UEitself and associated NAS identity (e.g. S-TMSI) to AS layer of therelay UE (e.g. adaptation layer) and/or provides the received NASmessage of the remote UE and associated NAS identity of remote UEsimultaneously to AS layer.

When the NAS layer of the relay UE triggers service request for theremote UE by providing associated remote UE's NAS identity (e.g. S-TMSI)to AS layer of the remote UE (e.g. adaptation layer) with providingservice request for relay UE itself (Model B), the RRC layer of therelay UE sends the RRC connection request message of the relay UE itselfwith the relay UE's NAS identity and the relay UE sends the receivedcause value and call type to RRC layer of the relay UE (S1107).

After RRC connection is setup (i.e. RRC connection setup message isreceived from the network), the relay UE sends RRC connection setupcomplete for the relay UE and the remote UE including the relay UE's NASmessage and the remote UE's NAS message in the same message (ordifferent message) to the RAN node (e.g. eNB (S1109).

In the RRC connection complete message, the relay UE includes the NASidentity of the remote UE and the cause value of the remote UE.

Meanwhile, when the NAS layer of the relay UE triggers service requestfor the remote UE by providing associated remote UE's NAS identity (e.g.S-TMSI) to AS layer of the remote UE (e.g. adaptation layer) withoutproviding service request for relay UE itself (Model C), the RRC layerof the relay UE sends the RRC connection request message with the remoteUE's NAS identity to the RAN node (e.g. eNB) (S1111).

After RRC connection is setup (i.e. RRC connection setup message isreceived), the relay UE sends the NAS message of the remote UE to theeNB (S1113).

In this case (steps of S1111 and S1113), the relay UE makes an RRCconnection with eNB but does not establish a connection with the corenetwork because the NAS layer of the relay UE does not send a relay UE'sNAS message (e.g. service request).

Since the service request of the relay UE not indicated by the NAS layerof the relay UE, only the RRC connection between the relay UE and theeNB is established, and the EPS bearer between the relay UE and the corenetwork is not established. On the other hand, in case of steps of S1107and S1109, an EPS bearer is established between the UE and the corenetwork section for both the relay UE and the remote UE.

The step of S1111 can avoid unnecessary signaling from the core networkbecause there is no data of the relay UE in the view point of the relayUE. However, in order to transmit the message of the remote UE, therelay UE also needs to transit to the RRC connection state.

And the network transmits RRC connection setup message of the remote UEvia the relay UE (S1115). In this case, after RRC connection is setup(i.e. RRC connection setup message is received) by the remote UE, theremote UE doesn't need to send the RRC connection setup complete messageto the eNB via relay UE. This is because the information related to RRCconnection setup complete message has already been transmitted throughstep S1101.

FIG. 12 is a conceptual diagram for performing a RRC connectionestablishment procedure depending on sidelink condition by a remote UEin wireless communication system according to embodiments of the presentinvention.

It is proposed of the method of differentiating the RRC connectionestablishment procedure depending on sidelink condition. If the sidelinkcondition of the remote UE is not met, the remote UE uses the first RRCconnection establishment procedure while if the sidelink condition ofthe remote UE is met, the remote UE uses the second RRC connectionestablishment procedure.

The sidelink condition means: i) there is any discovered relay UE, orii) there is established PC5 connection between the relay UE and theremote UE, or iii) there is paired connection between the relay UE andthe remote UE.

First RRC connection establishment includes an existing RRC connectionprocedure which is using RRC connection request, RRC connection setup,RRC connection setup complete message, or an existing RRC connectionprocedure which is using RRC connection resume request, RRC connectionresume, RRC connection resume complete message.

Second RRC connection establishment includes a new RRC connectionestablishment procedure which is using the reduced number of messagesfor RRC connection establishment procedure such as one/two stepsprocedure.

In case one or two steps procedure is used, for instance, the firstmessage includes the contents of first RRC message used toestablish/resume RRC connection (e.g. RRC connection request, RRCconnection resume request) and third RRC message (e.g. RRC connectionsetup complete, RRC connection resume complete).

Since the first RRC message is used to include the fields in theexisting Msg.5 (RRC connection setup complete), transmission of thethird RRC message (e.g. RRC connection setup complete, RRC connectionresume complete) can be skipped. With this, it is possible to reduce thenumber of message exchanges so that the remote UE and relay UE areallowed to save the battery.

The example of the signaling flow for the above methods is as FIG. 12.

When there is no sidelink connection between remote UE and relay UE, ifthe remote UE needs to establish RRC connection, the RRC connectionrequest, RRC connection setup and RRC connection setup completeprocedure is used (A).

When there is established sidelink connection between remote UE andrelay UE, if the remote UE needs to establish RRC connection, thesimplified RRC connection procedure is performed by the remote UE (B).

With this methods, the remote UE is able to reduce the number of messageexchanges for RRC connection establishment so that the remote UE is ableto save the power of the remote UE.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from essential characteristics of the presentinvention. The above embodiments are therefore to be construed in allaspects as illustrative and not restrictive. The scope of the inventionshould be determined by the appended claims, not by the abovedescription, and all changes coming within the meaning of the appendedclaims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

The invention claimed is:
 1. A method performed by a relay userequipment (UE) operating in a wireless communication system, the methodcomprising: receiving a first Radio Resource Control (RRC) connectionrequest message for establishing RRC connection of a remote UE from theremote UE which is configured to connect to the relay UE via sidelink,wherein the first RRC connection request message includes a servicerequest message, an identity of the remote UE, a cause value, a calltype, and Non Access Stratum (NAS) information, wherein the cause valueand the call type are provided by a first RRC layer of the remote UE,and the cause value and the call type are included in a header of thefirst RRC connection request message by a first adaptation layer of theremote UE, wherein based on the relay UE being in RRC idle state, asecond adaptation layer of the relay UE forwards the NAS information,the cause value and the call type to a NAS layer of the relay UE, onlywhen an indication indicates that the NAS information is included in thefirst RRC connection request message, wherein the NAS information, thecause value and the call type are de-capsulated by a second RRC layer ofthe relay UE, and wherein the indication is included in the first RRCconnection request message by the first adaptation layer, wherein theNAS layer of the relay UE triggers service request for the remote UE bytransmitting the NAS information, the cause value and the call type tothe second adaptation layer; transmitting a second RRC connectionrequest message with the identity of the remote UE to an eNB;transmitting a first RRC connection setup message for the remote UE tothe remote UE, after receiving a second RRC connection setup message forthe relay UE from the eNB; and transmitting a RRC connection setupcomplete message with the NAS information to the eNB.
 2. The methodaccording to claim 1, wherein based on the NAS information forestablishing RRC connection of the remote UE further includinginformation related to a RRC connection setup complete message (Msg.5),the relay UE doesn't need to receive the RRC connection setup completemessage from the remote UE to forward it to the eNB after RRC connectionis setup by the remote UE.
 3. The method according to claim 1, whereinbased on the second adaptation layer forwarding the received NASinformation to the NAS layer of the relay UE, the second adaptationlayer doesn't store the received NAS information.
 4. The methodaccording to claim 1, wherein the remote UE is connected to a corenetwork while the relay UE is not connected to the core network so thatthere is no establishment of EPC bearers between the relay UE and thecore network.
 5. The method according to claim 4, wherein based on theNAS layer of the relay UE triggering service request for the relay UE inaddition to the service request for the remote UE, the relay UE isconfigured to be connected to the core network so that there isestablishment of EPC bearers between the relay UE and the core network.6. The method according to claim 1, wherein the relay UE relays databetween the remote UE and the eNB.
 7. A relay User Equipment (UE)configured to operate in a wireless communication system, the relay UEcomprising: a Radio Frequency (RF) module; and a processor operablycoupled with the RF module and configured to: receive a first RadioResource Control (RRC) connection request message for establishing RRCconnection of a remote UE from the remote UE which is configured toconnect to the relay UE via sidelink, wherein the first RRC connectionrequest message includes a service request message, an identity of theremote UE, a cause value, a call type, and Non Access Stratum (NAS)information, wherein the cause value and the call type are provided by afirst RRC layer of the remote UE, and the cause value and the call typeare included in a header of the first RRC connection request message bya first adaptation layer of the remote UE, wherein based on the relay UEbeing in RRC idle state, a second adaptation layer of the relay UE isconfigured to forward the NAS information, the cause value and the calltype to a NAS layer of the relay UE, only when an indication indicatesthat the NAS information is included in the first RRC connection requestmessage, wherein the NAS information, the cause value and the call typeare de-capsulated by a second RRC layer of the relay UE, wherein theindication is included in the first RRC connection request message bythe first adaptation layer, wherein the NAS layer of the relay UE isconfigured to trigger service request for the remote UE by transmittingthe NAS information, the cause value and the call type to the secondadaptation layer; transmit a second RRC connection request message withthe identity of the remote UE to an eNB, transmit a first RRC connectionsetup message for the remote UE to the remote UE, after receiving asecond RRC connection setup message for the relay UE from the eNB, andtransmit a RRC connection setup complete message with the NASinformation to the eNB.
 8. The relay UE according to claim 7, whereinbased on the NAS information for establishing RRC connection of theremote UE further including information related to a RRC connectionsetup complete message (Msg.5), the relay UE doesn't need to receive theRRC connection setup complete message from the remote UE to forward itto the eNB after RRC connection is setup by the remote UE.
 9. The relayUE according to claim 7, wherein based on the second adaptation layerforwarding the received NAS information to the NAS layer of the relayUE, the second adaptation layer doesn't store the received NASinformation.
 10. The relay UE according to claim 7, wherein the remoteUE is connected to a core network while the relay UE is not connected tothe core network so that there is no establishment of EPC bearersbetween the relay UE and the core network.
 11. The relay UE according toclaim 10, wherein based on the NAS layer of the relay UE triggeringservice request for the relay UE in addition to the service request forthe remote UE, the relay UE is configured to be connected to the corenetwork so that there is establishment of EPC bearers between the relayUE and the core network.
 12. The relay UE according to claim 7, whereinthe relay UE is configured to relay data between the remote UE and theeNB.
 13. The method according to claim 1, wherein the relay UE iscapable of communicating with at least one of another UE, a UE relatedto an autonomous driving vehicle, a base station and/or a network. 14.The UE according to claim 7, wherein the relay UE is capable ofcommunicating with at least one of another UE, a UE related to anautonomous driving vehicle, a base station and/or a network.